Create 92-reverse-linked-list-ii.js

Author: everthis

92-reverse-linked-list-ii.js

@@ -0,0 +1,52 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @param {number} m
+ * @param {number} n
+ * @return {ListNode}
+ */
+const reverseBetween = function(head, m, n) {
+    // Empty list
+    if (head == null) {
+        return null;
+    }
+
+    // Move the two pointers until they reach the proper starting point
+    // in the list.
+    let cur = head, prev = null;
+    while (m > 1) {
+        prev = cur;
+        cur = cur.next;
+        m--;
+        n--;
+    }
+
+    // The two pointers that will fix the final connections.
+    let con = prev, tail = cur;
+
+    // Iteratively reverse the nodes until n becomes 0.
+    let third = null;
+    while (n > 0) {
+        third = cur.next;
+        cur.next = prev;
+        prev = cur;
+        cur = third;
+        n--;
+    }
+
+    // Adjust the final connections as explained in the algorithm
+    if (con != null) {
+        con.next = prev;
+    } else {
+        head = prev;
+    }
+
+    tail.next = cur;
+    return head;
+};